Method for the verification of the polarity, presence, alignment of components and short circuits on a printed circuits board

ABSTRACT

The invention relates to a method for the verification of the presence and proper orientation of a component on a printed circuit board. The board has a plurality of areas for receiving a component respectively. Each area is marked in the center thereof with a first marker. Adjacent each area, and indicative of the polarity of the component, a second marker is marked on the board. The presence or absence of a component can be evaluated by inspecting the board after it has been populated and determining whether any of the first markers appear, indicating that a component is missing. Verification of the polarity of a component is done by placing a marker on a portion of a component required to be installed in a predetermined position indicative of polarity. Inspection of the board once it has been populated will determine if the component is in the proper orientation by verifying if the second marker and the marker on the component are in alignment. Preferably, the first marker and the second marker are of different colours, and are preferably UV compatible layers. Additionally, the method of the invention, when applied between the leads of a multi-legged component or between discrete components, such as by the etching of additional portions of the solder mask or by adding an additional layer, will produce a shadow on the reflective surface, thereby identifying a short at that location.

RELATED APPLICATION

This application is a continuation-in-part of application Ser. No. 09/247,811 filed on Feb. 11, 1999, now U.S. Pat. No. 6,272,018 B1.

FIELD OF THE INVENTION

The present invention relates to the verification of the polarity, presence, alignment of components installed on a printed circuit board as well as short circuits present on a printed circuit board.

DESCRIPTION OF THE PRIOR ART

Printed circuit boards are increasingly populated with greater component density. A typical printed circuit board can house hundreds, if not thousands of components, some of which require installation in a predetermined orientation, i.e. polarity.

Along with the increase in numbers of components on a printed circuit board, the task of inspecting each board for the presence and alignment of a component solder shorts, and the proper orientation of given components has also become more complex. The inspection task is usually done by visually inspecting a board, either after the board has been populated, or if the board has been returned for a malfunction. Inspectors quickly become fatigued and stressed when performing this task, particularly when dealing with densely populated printed circuit boards. The inspection task is also labour-intensive.

There is thus a need for a simpler and more economical process for inspecting printed circuit boards for the presence and correct orientation or polarity of components, solder integrity and alignment.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a simpler and more economical method for the verification of the presence or alignment of a component on a printed circuit board.

In accordance with the invention, this object is achieved with a method for the verification of the presence of a component on a printed circuit board, comprising the steps of:

a) providing a printed circuit board having a plurality of areas, each area being adapted to receive a component;

b) marking at least a portion of each of said areas with a marker;

c) installing each of said components in their respective areas; and

d) inspecting said printed circuit board for the presence of a marker, the presence of a marker indicating that a component is missing or that the component is out of alignment.

It is also an object of the invention to provide a simpler and more economical method for the verification of the orientation of a component on a printed circuit board. In accordance with the invention, this object is achieved with a method for the verification of the orientation of a component on a printed circuit board, comprising the steps of:

a) providing a printed circuit board having a plurality of areas, each area being adapted to receive a component, at least one of said components requiring installation in a predetermined position indicative of the polarity of the component;

b) marking said printed board with at least one marker adjacent an area for receiving a component in said predetermined position;

c) marking a portion of at least one component to be installed in said predetermined position, said marking being indicative of the polarity of said component;

d) installing said components on said printed circuit board;

e) inspecting said printed circuit board for markers on said printed circuit board and on said components, said component requiring installation in a predetermined position being installed in said predetermined position when said marker on said printed circuit board adjacent said area and said marker on said portion of said component are in alignment.

It is a further object of the invention to provide a simpler and more economical method for the verification of shorts on a printed circuit board. In accordance with the invention, this object is achieved with a method for the verification of shorts on a printed circuit board comprising the steps of:

(a) providing a printed circuit board having a plurality of areas, each area being adapted to receive a component;

(b) marking at least a portion of each of said areas with a marker;

(c) installing each of said components in their respective areas; and

(d) inspecting each of said printed circuit boards for the identification of shorts between solder pads of components.

The invention is also concerned with a printed circuit board marked according to the above methods.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention and its advantages will be more easily understood after reading the following non-restrictive description of preferred embodiments thereof, made with reference to the following drawings, in which:

FIG. 1 is a schematic representation of an unpopulated printed circuit board marked according to a preferred embodiment of the invention;

FIG. 2 is a schematic representation of the components for populating the printed circuit board of FIG. 1;

FIG. 3 is a schematic representation of a correctly populated printed circuit board;

FIG. 4 is a schematic representation of an incorrectly populated printed circuit board, where all of the components are installed, but some are not installed in the correct orientation;

FIG. 5 is a schematic representation of an incorrectly populated printed circuit board, where some of the components are missing; and

FIG. 6 is a schematic representation of an integrated circuit where shorts are identified.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Referring now to FIG. 1, the invention is concerned with a method for the verification of the polarity and presence of components on a printed circuit board 1. The printed circuit board 1 is provided with a plurality of areas 10, each of which is designed to receive a component 20.

In order to determine if all of the components have been installed on the printed circuit board, also referred to as populating the board, each area 10 is provided with a marker 30, preferably in the center thereof. The marker 30 could be paint, etching, glue, coating or any other type of marking, but is preferably a marker which provides a UV signature. Also preferably, the UV marker is permanently accessible on the PCB and will not fade over time. It should be understood that although the present invention contemplates a layer or physical marking on a PCB, another solution is also possible. The present invention contemplates creating the marker by etching or designing the board in such a way that a UV compatible layer which forms part of most commercially available PCBs is exposed. It should be noted that ceramic PCBs and power PCBs may not be provided with such a UV compatible layer.

It should be understood that a UV compatible layer means a layer which absorbs or reflects UV light, so that it can be readily distinguished when a UV light is shone on it.

The PCB is made of a plurality of layers, including a substrate (which can itself be a plurality of layers), a layer, which is UV compatible layer, and a solder resist. The invention contemplates etching away additional portions of the solder resist of the PCB or designing the PCB such that this UV compatible layer which is present on most PCBs is revealed.

Once the printed circuit board 1 has been marked, the components are installed in their respective areas. Finally, the board 1 is visually inspected. If the board is marked with the UV reflecting coating or the board is etched to reveal the UV compatible layer, a UV light is shined on the board. If the board is completely populated in that there are no components missing, no markers 30 will appear during inspection, as can be seen in FIG. 3. However, if one or more components are missing, as shown in FIG. 5, the markers 30′ will appear when the UV light is shone on the board. Consequently, a detailed visual inspection of a printed circuit board is no longer necessary, since it will be rapidly determined if a component is missing due to the presence, or absence of the markers 30.

It should be noted that the marking which is applied to the surface of a printed circuit board, when viewed under UV light or, alternatively, infrared radiation, radiates a signature. This also applies to a marking applied to a component.

The invention is also concerned with a method for verifying if a component has been placed in its proper orientation. Most components for populating a printed circuit board need to be placed in a predetermined position, indicative of the polarity of the component. If a component is not properly placed, the printed circuit board will not function properly, or the component will often have a reduced life span by virtue of this incorrect placement. Present components are provided with a notch which is indicative of the polarity of the component. However, when dealing with densely populated boards 1, it is often difficult to identify the notch. Furthermore, there is often no proper frame of reference on the board to verify if the component has been placed in the proper orientation.

In accordance with the invention and as shown in FIGS. 1, 3 and 4, the board is further provided with another marker 40, located adjacent an area 10, but indicative of the position of the component to be placed therein. Each component 20 is also marked with a marker or indicator 40′, indicative of the polarity of the component 20. Preferably, markers 40 and indicators 40′ are of the same colour, but of a different colour from marker 30 used to indicate the presence or absence of a component on a board 1. As with marker 30, markers 40 and indicators 40′ could be paint, etching or any other type of markings, but are preferably a UV reflecting coating. Also preferably, the UV coating is cured into the component 20 so that it will not fade over time.

The correct orientation of a component on a board is determined when markers 40 and 40′ are in alignment, as illustrated in FIG. 3. However, in FIG. 4, markers 41 (on each component) and 42 (on the board 1) are not in alignment, indicating that the component is not in the proper orientation.

The present invention also concerns the identification of shorts on a printed circuit board. Multi-leaded components, such as integrated circuits, have leads or pins that are getting thinner and are gapped closer together, so that the chance for shorts due to solder bridging is increasing (see FIG. 6). By the removal of additional portions of the solder resist or by the addition of a UV reflective material in between and around these sensitive areas, the method of the present invention will permit easy identification thereof. When these areas are irradiated with a UV or other compatible source, the illuminated material identifies such shorts as a shadow or other visible mark.

The invention thus simplifies the process required to fully inspect the orientation/alignment as well as the presence or absence of components on a printed circuit board and the identification of shorts. The invention also significantly improves the efficiency of quality control inspection by reducing fatigue and other emotional stresses suffered by inspectors. Finally, the invention reduces the number of inspectors required to perform inspection of printed circuit boards, and the quality of the printed circuit board is improved.

Although the present invention has been explained hereinabove by way of a preferred embodiment thereof, it should be pointed out that any modifications to this preferred embodiment within the scope of the appended claims is not deemed to alter or change the nature and scope of the present invention. 

What is claimed is:
 1. A printed circuit board having a plurality of areas, each of said areas being adapted to receive a component, each of said areas being marked with a marker, wherein said marker is a portion of a UV compatible layer in said printed circuit board that is exposed by etching, whereby, in use, when said components are installed in said areas, said components cover said markings so that the absence of a component in an area can be visually detected, the presence of a marker indicating that a component is missing.
 2. A printed circuit board having a plurality of areas, each area being adapted to receive a component, at least one of the components requiring installation in a predetermined position indicative of the polarity of the component, the at least one area for receiving the at least one component requiring installation in the predetermined position being marked with a marker adjacent the area and indicative of the polarity of the component, whereby the at least one component requiring installation in a predetermined position is marked with a marker, so that when said components are installed on said printed circuit board, correct polarity of each component requiring installation in said predetermined position can be determined by inspecting the printed circuit board to determine that the marker adjacent the at least one area and the marker on the corresponding component are in alignment.
 3. A printed circuit board according to claim 2, wherein said marker adjacent said area and said marker on said component is paint.
 4. A printed circuit board according to claim 3, wherein said marker adjacent said area and said marker on said component is a UV reflective coating.
 5. A printed circuit board according to claim 2, wherein said marker is a portion of said printed circuit board that has been etched away to reveal a UV compatible layer.
 6. A printed circuit board according to claim 2, wherein each of said areas of said printed circuit board is marked with another marker.
 7. A printed circuit board according to claim 6, wherein said marker adjacent the at least one area is of a first color, and said another marker is of a second color.
 8. A method for the verification of the presence of a component on a printed circuit board, comprising: a) providing a printed circuit board having a plurality of areas, each area being adapted to receive a component; b) marking at least a portion of each of said areas with a marker by uncovering a portion of said printed circuit board such that said uncovered portion of said printed circuit board reveals a UV reflecting layer; c) installing a plurality of components each in its respective area; and d) inspecting said printed circuit board for the presence of a marker by shining UV light on said printed circuit board, the presence of a marker indicating that a component is missing.
 9. A method according to claim 1, wherein said method further comprises: a) marking said printed board with at least one marker adjacent an area for receiving a component in a predetermined position; b) marking with an indicator a portion of at least one component requiring installation in said predetermined position; and c) inspecting said printed circuit board for markers on said printed circuit board and indicators on said components, a component requiring installation in a predetermined position being installed in said predetermined position when said marker on said printed circuit board adjacent said area and an indicator on said portion of said component are in alignment.
 10. A method according to claim 9, wherein said method further includes the step of marking each portion of each of said areas with a first color, and marking said printed circuit board and said component requiring installation in said predetermined area with a second color.
 11. A method according to claim 10, wherein said first color and said second color are UV reflecting coatings.
 12. A method for the verification of the orientation of a component on a printed circuit board, comprising: a) providing a printed circuit board having a plurality of areas, each area being adapted to receive a component, at least one of a plurality of components requiring installation in a predetermined position indicative of the polarity of the component; b) marking said printed board with at least one marker adjacent an area for receiving a component in said predetermined position; c) marking with an indicator a portion of at least one component to be installed in said predetermined position, said indication being indicative of the polarity of said component; d) installing a plurality of said components on said printed circuit board; e) inspecting said printed circuit board for markers on said printed circuit board and indicators on said components, a component requiring installation in a predetermined position being installed in said predetermined position when a marker on said printed circuit board adjacent said area and an indicator on said portion of said component are in alignment.
 13. A method according to claim 12, wherein said marker on said printed circuit board adjacent said area and said indicator on said portion of said component are paint.
 14. A method according to claim 12, wherein said marker is a UV reflecting coating, and said step of inspecting said printed circuit board further includes the step of shining a UV light on said printed circuit board.
 15. A method according to claim 12, wherein said step (b) of marking a portion of each of said areas comprises the step of etching away a portion of said printed circuit board to reveal a UV reflecting layer, and wherein said step of inspecting said printed circuit board further includes the step of shining a UV light on said printed circuit board.
 16. A method for the verification of shorts on a printed circuit board comprising the steps of: (a) providing a printed circuit board having a plurality of areas, each area being adapted to receive a component; (b) marking at least a portion of each of said areas with a marker; (c) installing each of said components in their respective areas; and (d) inspecting said printed circuit board for the identification of shorts between solder pads of components said step of inspecting including the step of shining a UV light on said printed circuit board, a short being identified as a shadow against a white background. 